Housing for containing a fragile element such as a logic circuit

ABSTRACT

A housing designed to contain a logic circuit (15) comprising two shells (11a, 11b) each including a welding area (17a, 17b) having an appropriate geometry permitting ultrasonic welding, such that when both shells are assembled before a welding phase, they are shifted along a vertical axis (20). The supporting plate (13) comprises a mounting ear (23) while the shells comprise a receptacle (33a, 33b). During the welding phase, there is no concomitant contact between any of the upper face (26) and lower face (27) of the ear (23) and the corresponding bearing faces (34a, 34b) of the receptacles, owing to a shift (21). The shift is reduced and the concomitant contact takes place between the bearing faces (34a, 34b) of the receptacles and each of the upper and lower faces (26, 27) of the ear (23) only when the welding phase is completed.

BACKGROUND OF THE INVENTION

This invention provides a housing designed to contain at least onefragile element, such as a logic circuit and to a process for providingan assembly process for such a housing.

More particularly, this invention relates to a housing exhibiting theshape of a credit card and is in the spirit of the expansion of logiccircuit cards liable to fulfil several functions such as access cards tocontrolled areas, bank cards or others.

FIELD OF THE PRIOR ART

Generally, the housings according to the invention comprise two shellsand a supporting plate designed to carry a logic circuit. As regards thespecific expansion also aimed at by the instant invention, the housingexhibits the shape of two generally plane shells, exhibiting, generally,the shape of a credit card, while the supporting plate also includes aconnector designed for permitting the connection of the card logic to anexternal logic circuit, the shells and the supporting plate arepreferably made of plastics.

The general technical problem which was encountered by the Applicant isthat of the final assembly of the shells and supporting plate.

Various solutions are known. They all resort to adhesive-bondingtechniques implementing either adhesive or adhesive-coated films. Thosetechniques present various drawbacks.

First, the adhesive efficiency is not always satisfactory since thematerials to be brought together are not always clean and perfectlyplane. Effectively, the adhesive bonding depends upon the surface energyof the adhesive and that of the materials to be bonded by adhesive. Theadhesive surface energy is usually constant; but, that of the materialsto be bonded by adhesive is liable to change from one manufacturingbatch to another. It is therefore rather difficult to reproduce from onebatch to another similar adhesive bonding conditions, what requires aspecific processing of the batches and, in addition to the economicaldrawbacks, renders the adhesive bonding characteristics hazardous.

Another drawback is that bonding by means of adhesive can be easilydamaged especially when the card is submitted to large temperaturevariations. In this respect, the cards aimed at by the instant inventionhave to be capable of withstanding temperature variations of about 100°C. Similarly, the cards according to the invention have to be capable ofwithstanding large mechanical stresses. Since, in addition, the variousadhesives which are marketed have their own advantages and drawbacks, itis often difficult to comply with the multiple requirements imposed bythe specifications sheet as, for example, low temperature resistance,bending strength, resistance to solvents, to pollution, etc.

Finally, the adhesive implementation is not in any case easy. Indeed,those skilled in the art are faced with pollution problems as regardscomponents or mankind. They are also faced with adhesive bonding timeproblems which are not always easy to control in an assembly line.Ultrasonic welding is also known.

This technique, which permits bringing together of plastic elements byfusing the material at the connection point, eliminates some of thedrawbacks hereinabove mentioned. However, as regards the assembly of ahousing containing a fragile logic circuit, and more particularly whensaid housing exhibits the general shape of a relatively thin creditcard, those skilled in the art cannot, in the present state of thetechnique, consider to use an ultrasonic welding method.

The basis of the method is to set in vibration, at an ultrasonicfrequency (in the range of 20 to 50 KHz) the welding area, in thepresent application, the periphery of the plane housing. Therefore, incase one would resort to such an assembly method according to the knowntechniques, the vibrations would be transmitted to the whole housing.Regarding the present application relative to the assembly of two planeshells between which a logic circuit is sandwiched, the vibrations wouldbe transmitted to the logic circuit, what would practically result inthe destruction of the fragile elements included in this circuit. Thiswould also be true in case the supporting plate of the circuit includesa connector. Numerous welding connections are then provided between thelogic circuit elements and conductor pins, those weldings being exposedto be destroyed or, at least damaged, in case they would be submitted,even for a very short lapse of time, to vibrations of the hereinabovementioned type.

This is the reason why, in a first step, the Applicant has conductedexhaustive studies in the field of adhesive-bonding techniques. However,in spite of the fact that, for those skilled in the art, the ultrasonicwelding method seemed to be utterly improper to solve the assemblyproblem for the reasons that have been disclosed hereinabove, theApplicant has undertaken studying a solution permitting to obtain theassembly by means of ultrasonic welding, while preventing as far aspossible the ultrasonic vibrations having a damaging amplitude frombeing transmitted to the fragile elements which must be contained in thehousing, whether they are certain logic circuit elements, weld seams ofthe connector or any other fragile element. At the same time, theApplicant has continued its experimentations for improvingly complyingwith the technical characteristics imposed by the specifications sheetas regards the logic circuit carrier cards, especially their bendingcapacity.

The instant invention provides for a solution to this double technicalproblem since it aims at providing a housing designed to contain,especially, at least one fragile element such as a logic circuit,comprising at least two shells which have to be assembled by means ofultrasonic welding, each shell comprising for this purpose at least onewelding area, having an appropriate geometry for permitting theultrasonic welding, and being such that when both shells are assembled,before the welding phase, a shift directed along a first axis, calledvertical axis, generally separates the shells. The fragile element ismounted on at least one supporting plate comprising at least a mountingportion while one at least of the shells comprises a receptacle for thisportion, the shells, said receptacle and mounting portion cooperating sothat, on the one hand, the movement of the supporting plate along bothaxes, respectively called transversal and axial axes, is limitedrespectively to a transversal and axial clearance and, on the otherhand, after the welding phase, the movement of the supporting plate,along the vertical axis, is limited to a vertical clearance.

The instant invention also aims at providing for a housing assemblymethod such as the one succinctly described hereinabove, consisting in:

preassembling both shells and the supporting plate,

pressing the shells together by means, in particular, of an ultrasonicwelding device,

setting the welding area in vibration by means of a welding device bydirecting the ultrasonic vibrations according to said vertical axis,

stopping the vibrations as soon as said shift according to the verticalaxis is cancelled.

Owing to those arrangements, a housing is carried out, containing atleast one fragile element which can be assembled by means of ultrasonicwelding. Thereby, the drawbacks inherent to the "adhesive-bonding" typetechniques are eliminated. Moreover, as regards the credit card-shapedhousing developed by the Applicant, the requirements imposed by thespecifications sheet are better complied with.

Therefore, as regards the resistance of the whole set to the ultrasonicvibrations, during the welding phase, it must be noted that owing to theshift between the shells at the beginning of the welding phase accordingto a so-called vertical axis, parallel to the amplitude of thevibrations, one prevents them from being directly transmitted to thesupporting plate and, therefore, to the fragile elements carried by saidplate.

It will be further noted that the mounting portion of the supportingplate is imbedded and not welded in the receptacle. Moreover, at leastin some applications, a slight clearance is provided so that themounting portion of the supporting plate is liable to move towardsvarious directions inside the receptacle, during and after the weldingphase. The advantage of those arrangements is to further reduce thetransmission points of the vibrations between the shells and theassembly portion. It is easy to understand that if one can avoidblocking, by a clearance-free imbedding, the mounting portion of thesupporting plate, one avoids at the same time to get the vibrationstransmitted directly or indirectly through the imbedding means.

On the other hand, according to the invention, a homogeneous housingcomprising no foreign elements and no interfaces between the shells iscarried out. Such a housing functions in an homogeneous manner undervarious atmospheric or climatic conditions. Thus, the assembly processpermits to extend the resistance of the card-shaped housing whether bylow or by high temperatures, the storage range increasing from -40° C.,+85° C. according to the prior art techniques to -55° C., +150° C. oreven more if necessary, in accordance with the materials used. Moreover,if it is deemed desirable, a real airtight ability of the card isobtained after welding.

Another advantage of the invention is the presence of a slight clearanceafter the welding phase, especially in a vertical direction but also,when it is possible, in the axial and transversal directions. Thisclearance permits, as regards the housing exhibiting the general shapeof a credit card, to improve the ability of the housing to withstandbendings. Indeed, when the housing is submitted to a flexion, the logiccircuit, which most frequently exhibits the shape of a small planeprinted circuit, can shift within determined directions, thuscompensating for at least a portion of the bending.

The manufacturing problems hereinabove mentioned are then solved sincethe assembly process is clean and rapid, non-pollutive, and the assemblyconditions are reproducible, without hazard.

Finally, the above mentioned advantages have a major financialrepercussion since the manufacturing time (the welding phase lasts onlya few milliseconds), the automatization and, in a general manner, theease of the method, permit to optimize the costs.

In some applications, it is not desirable, once the whole set has beenassembled and welded, that the supporting plate be capable of movingtowards one or several directions. That is the reason why, in someapplications of the invention, one at least of the transversal, axialand vertical clearances is null. However, according to the invention,the vertical clearance can be cancelled only once the welding phase iscompleted, in order to avoid that the ultrasonic vibrations be directlytransmitted to the supporting plate during the welding phase.

In a preferred embodiment, the mounting portion comprises a mountingear, roughly parallel-epipedic, generally extending according to atransversal-axial plane, while the receptacle has a similar shape, therelative size of the supporting plate, mounting ear and receptacle beingsuch that, on the one hand, the height of the ear is at least equal tothe total height of the receptacle of this ear once the housing isassembled and welded and, on the other hand, since the ear comprises, atits transversal end closest to the welding area, a lateral facepositioned according to an axial-vertical plane, no contact is possiblebetween this lateral face and the corresponding face of the receptacle.

Those arrangements are particularly simple to implement and moreover thevibrations cannot be transmitted either directly or indirectly by saidlateral face.

According to another characteristic of this preferred embodiment, eachshell comprises a notch adapted to receive the supporting plate, whilethe latter comprises two mounting portions, each of those mountingportions being associated with an end lateral face of the supportingplate, the notch comprising itself two corresponding lateral faces, therelative size of the notch and of the supporting plate is such that noconcomitant contact is possible between each other, since the endlateral faces of the supporting plate cannot be simultaneously incontact with the corresponding faces of the notch.

Those arrangements permit to especially avoid, during the welding phase,that the supporting plate get imbedded and blocked in a transversaldirection and therefore that the vibrations be transmitted more or lessindirectly to the supporting plate by means of its end lateral faces.

In this embodiment, the supporting plate is blocked in the axialdirection, each of the mounting ears exhibiting a front face and a rearface extending according to a vertical-transversal plane and abuttingagainst the corresponding faces included in the receptacles. Thus, thevibrations possible transmitted by those faces mainly radiate accordingto an axial direction and are therefore substantially damped in thetransversal direction towards the inner part of the supporting plate.

Advantageously, the edges of the mounting ear are rounded up, whichpermits to especially avoid the peak effects and to further increase thedamping of the vibrations.

In this preferred embodiment, according to a particularly advantageouscharacteristic, the shells, on the one hand, and the mounting portion,on the other hand, are manufactured from distinct materials not liableto get amalgamated during an ultrasonic welding operation.

Thus, one prevents the mounting portion from getting accidentally weldedin the receptacle, which permits, on the one hand, to avoid transmittingthe vibrations through this accidental welding before the welding phaseis completed and, on the other hand, to avoid blocking the supportingplate when, for certain applications, it is desirable that the latter beable to move towards one or several directions, as hereinaboveexplained.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the instantinvention will clearly appear from the following detailed description ofpreferred embodiments, in connection with the attached drawings,wherein:

FIG. 1 is a perspective exploded view of an embodiment of a housingaccording to the invention;

FIG. 2 is a detailed section view of one of the shells and mountingportion of the supporting plate illustrated in FIG. 1, according to theline II--II of FIG 3;

FIG. 3 is a partial section view according to the line III--III of FIG.2, the shells being preassembled before welding;

FIG. 4 is a partial section view according to the line IV--IV of FIG. 2,the shells being preassembled before welding;

FIG. 5 is a diagram showing the damping of the vibrations transmitted tothe supporting plate during the welding phase;

FIG. 6 is a view similar to FIG. 3 but illustrates the whole set afterwelding; and

FIG. 7 is a view corresponding to FIG. 3 and illustrates an alternativeimplementation.

DETAILED DESCRIPTION OF THE DRAWINGS

According to the embodiment shown in FIGS. 1 to 4, a housing 10comprises two shells, a lower one, 11a, and an upper one, 11b, and asupporting plate 13, carrying a logic circuit, here shown in the shapeof a printed circuit 15. The shells 11a, 11b, are generally plane andtheir length and width correspond to the standard of the credit cards.

Each shell comprises, on one of its smaller sides, a receptacle 14a(14b), the shape of which is substantially rectangular, each of thosereceptacles being adapted to receive the supporting plate 13 whichprotrudes outside of the shells in this embodiment. The supporting plate13 also incorporates a connector, here comprising female plugsreferenced b1, b2 on the drawing. In the present embodiment, it is thefunction of the weld seams S1, S2, . . . Sn connecting the pins to thecircuit 15 to ensure the connection between the circuit 15 and thesupporting plate 13.

The instant invention relates to the mounting of the shells and thesupporting plate.

For this purpose, each shell comprises a welding area (17a, 17b), havingan appropriate geometry for permitting the ultrasonic welding.

In the described embodiment, the shells being manufactured from ABS,this welding area exhibits, on each of the shells 11a, 11b, a specificsection designed to permit and to facilitate this welding. On the lowershell 11a, the welding area 17a exhibits the shape of a sharp edge,while on the upper shell, the welding area 17b presents the shape of adepression exhibiting a substantially rectangular section (FIGS. 2 and3). Those areas 17a, 17b extend along the periphery of the shell, exceptfor the sides forming the notches 14a, 14b.

The geometry of the welding areas 17a, 17b can clearly be seen in FIG.3. According to a characteristic of the invention, the geometry of thewelding area of each of the shells is such that when both shells areassembled, before the welding phase, as shown in FIG. 2, they areshifted along a first, so-called "vertical", axis, here referenced 20.The shift of both shells is referenced 21 in FIG. 3.

The geometry of the welding area 17a, 17b illustrated in FIGS. 1 to 3 isnot the only possibility. Indeed, this shape depends, on the one hand,upon the material used (in the present embodiment, ABS) and, on theother hand, upon the size of the parts to be welded. Those skilled inthe art, who know the ultrasonic welding, will be able to determine theshape of the welding area to be adopted for each case. However,according to the invention, the adopted shape has to be designed so asto generate a shift along the axis 20 of both half shells, at least atthe mounting area of the supporting plate, as it will be apparent fromthe description thereof which is made hereinafter.

By way of example, FIG. 7 shows another shape that can be used if theshells are fabricated with nylon. It is noticeable that the weldingareas 17'a, 17'b exhibit a L-section but that at the start of thewelding phase an overlapping 17'c of the material generates a shift 21'.

According to the invention, the supporting plate 13 comprises at leastone mounting area. In the embodiment herein chosen and illustrated, themounting area is essentially constituted by a "mounting" ear, referenced23 in FIGS. 1 to 4. FIG. 1 shows that the supporting plate 13 comprisesan end lateral ear. Those ears are all identical and only the left one,shown in detail in FIGS. 2 to 4, will be described.

The mounting ear 23 is molded integral with the supporting plate 13. Itexhibits a general parallel-epipedic shape and is positioned on each endlateral face 24 of the supporting plate 13, substantially according to amid-plane schematized in FIG. 3 by the transversal axis 25.

The ear 23 comprises five external faces: an upper face 26, a lower face27, a lateral face 28, a front face 29 and a rear face 30.

The upper face 26 and the lower face 27 are generally plane and extendaccording to planes that are parallel to those of the shells 11a and11b. The lateral face 28 extends according to a plane substantiallyvertical, parallel to the axis 20. It is also parallel to thelongitudinal edges of the shells. The front face 29 and rear face 30 arepositioned vertically and perpendicularly with respect to thehereinabove described faces.

According to the invention, at least one of the shells 11a, 11bcomprises a receptacle for the mounting portion.

In the embodiment chosen and illustrated here, each shell comprises sucha receptacle (references 33a, 33b). Each of the receptacles 33a, 33bcomprises a horizontal bearing face 34a, (34b), a lateral face 35a(35b), a vertically extending front face 36a, (36b) and a verticallyextending rear face 37a, (37b).

According to an aspect of the invention implemented in the describedembodiment, FIGS. 2 and 4 show that the distance separating the frontface 29 and rear face 30 from the ear 23 is the same as the oneseparating the front face 36a, 36b and the rear face 37a, 37b from thereceptacles 33a, 33b, so that, according to a characteristic of anaspect of the invention implemented in this embodiment, the supportingplate 13 is blocked in the axial direction (schematized in FIG. 2 by theaxis 39).

According to another aspect of the invention, the ears 23 exhibit alateral extension (according to the transversal axis 25), substantiallylower than the lateral extension of the receptacles 33a, 33b. Similarly,the length of the supporting plate 13, between its end lateral faces 24,is substantially smaller than the distance between the lateral faces41a, 41b of the notch 14: thus, whether the housing is simply assembledbefore the welding phase (FIG. 3) or whether it is welded (FIG. 6). thesupporting plate 13 is capable of moving transversally (according to theaxis 25), and its movement is limited by the abutment of the supportingplate faces 24 against the lateral faces 41a, 41b of the notch.

It will be therefore noted, in the embodiment herein described andillustrated, and according to a particularly advantageous feature of anaspect of the invention, on the one hand, that no contact is possiblebetween the lateral face 28 of the ear 23 and the lateral face 35a or35b of the receptacle 33a or 33b and, on the other hand, that thesupporting plate 13 cannot get into contact with the shells 11a, 11bsimultaneously by means of each of its lateral faces 24.

According to the invention, the thickness of the ear 23, that is, thedistance separating its upper face 26 and lower face 27 is at leastequal to the distance separating its bearing horizontal faces 34a, 34bfrom the receptacles 33a, 33b when the shells are welded. In that case,when the welding phase is completed, there is a simultaneous contactbetween the upper face 26 and lower face 27 of the ear 23 respectivelywith the bearing face 34a of the lower shell 11a and the bearing face34b of the upper shell 11b. However, according to the embodiment chosenand illustrated here, the thickness of the ear 23 is chosen so as to besubstantially smaller than the distance separating the horizontal faces34a, 34b, once the welding is completed (FIG. 6). Thus, once the shellshave been welded, the supporting plate 13 is movable along the verticalaxis 20 but it is limited to the clearance JV illustrated in FIG. 6.

The assembly process will now be described.

First, as shown in FIGS. 3 and 4, one preassembles the shells 11a, 11band the supporting plate 13 on which the circuit 15 has been mountedbeforehand.

Then, in a way known per se, the shells 11a, 11b are positioned betweena supporting plate and a sonotrode so that a pressure is applied ontothe shells, this pressure being schematized in FIG. 4 by the arrows F.As shown in FIGS. 3 and 4, at the beginning of the welding phase, whilethe shells are assembled, the shells 11a, 11b are separated by the shift21. As a result, even though the thickness of the ear 23 issubstantially equal to the height of the whole receptacle 33a, 33b afterwelding, at the beginning of the welding phase, there is a verticalclearance at least equal to the shift 21 and the supporting plate canmove according to the vertical axis within the limits of this clearance.

As already disclosed, a transversal clearance is provided so that thelateral faces 24 of the supporting plate cannot get simultaneously incontact with the lateral faces 41a, 41b of the notches 14a, 14b.Moreover, no contact is possible between the lateral face 28 of the earand the lateral faces 35a and 35b of the receptacles 33a, 33b.

The sonotrode is then set in vibration. According to a characteristic ofthis method, the vibrations are directed according to a vertical plane(parallel to the axis 20). Therefore, the vibrations cannot be directlytransmitted to the upper face 26 and lower face 27 of the ear 23 sincesaid ear is not pinched between the shells. Similarly, for the reasonsmentioned hereinabove, none of the vibrations can be transmitted eitherby the lateral face 28 of the ear 23 or by the lateral faces 24 of thesupporting plate.

Thus, according to the implementation that is being described, at thebeginning of the welding phase, only the front face 29 and the rear face30 of the ear 23 are in contact with the corresponding faces of thereceptacle 33a or 33b (FIGS. 2 and 4). But, since the amplitude of thevibrations extend parallel to those faces and, in addition, since thosevibrations are in register one with respect to the other, the vibrationstransmitted by those faces are essentially propagated towards an axialdirection and substantially not towards a transversal direction.

In FIG. 5, the diagram shows the amplitude of the vibrations at thewelding seam 17a, 17b and the value of this amplitude as a function ofthe distance according to a transversal direction with respect to thearea 17a, 17b. In the area S1, the first welding (X-axis x_(S1) in FIG.5), the amplitude of the vibrations is substantially damped (amplitudeA_(S1)). Effectively, the Applicant has noticed that there is in x_(S1)a damping of about 40 dB with respect to the amplitude A_(max) of thevibrations in the welding region. Such a damping is sufficient in thepresent implementation to avoid damaging the welding S1. However, it isnoticeable that the farther one gets from the welding area, the higherthe damping is. In case elements still more fragile are to be assembledin a printed circuit, it will be sufficient, according to the embodimentherein described, to position them in a place where the damping is stillmore important.

The ultrasonic vibrations are applied for a relatively short time period(here, about a few tenths of a second). The vibration energy getsconcentrated on the edge 17a, in a well known manner, what causes thefusion of the material of this edge with the area 17b of the uppershell. Since a vertical pressure F is applied onto the shells, they getcloser, the shift 21 decreases and is then cancelled.

At the end of the welding phase, the welding edge 17a of the lower shell11a is entirely fused and the material that constituted this edge isengaged into the notch of the welding area 17b, as illustrated in FIG.6.

According to an advantageous characteristic of the invention such asimplemented in the present case, the vibrations are stopped as soon asthe shift 21 is cancelled. Owing to this arrangement, in case thethickness of the ear 23 is equal to the height of the whole receptacleset 33a, 33b after the welding phase, one avoids transmitting, even fora very short lapse of time, vibrations having an amplitude A_(max) tothe mounting ears 23 and to the supporting plate 13-circuit 15 set.

It is possible to further decrease the amplitude of the vibrations atthe fragile elements.

A first solution consists in suppressing the pinch of the ear 23 by itsfront and rear faces 29, 30, illustrated in FIGS. 2 and 4. It will thenbe possible to provide a slight axial clearance. However, later on, sucha clearance may prove to be damaging since the supporting plate 13 isthen allowed to slightly rotate according to a horizontal plane, what,in some implementations, may render it inappropriate to function as aconnector. Therefore, in the embodiment chosen and described here, ithas been deemed more advisable to maintain a contact between the frontface 29 and the rear face 30 of the ear 23 and the corresponding facesof the receptacles 33a, 33b.

As illustrated in the figures, it is also possible to provide a roundingof the horizontal edges of the ear 23. Owing to this arrangement, thepeak effect is then avoided, that is, the energy concentration on thoseedges, and a radiation of this energy towards the inner part of thesupporting plate when, for example, there is a contact between the lowerface 27 of the ear 23 and the bearing face 34a of the receptacle 33a ofthe lower shell 11a.

Moreover, in the embodiment chosen and illustrated here, according to anadvantageous characteristic of an aspect of the invention, thesupporting plate, as well as the mounting ear 23, is molded out ofnylon, this material being unlikely to get amalgamated with the ABSduring the welding phase. One therefore avoids to get the supportingplate 13 blocked in position, what permits to maintain the free movementof the supporting plate after the welding phase, according to verticaland transversal axes. Moreover, one avoids that, by carrying out amicrowelding on the front face 29 or rear face 30 and therefore blockingthe supporting plate, the vibrations get transmitted with a highamplitude towards the fragile elements carried by the supporting plate13.

It will be noted on the other hand that leaving a slight clearance inthe vertical and transversal directions permits to improve the abilityof the card to withstand bending stresses. Indeed, if the card issubstantially bent, the whole circuit is able to move, within the abovementioned clearance limits, to compensate as much as possible for thebending.

Of course, the instant invention, herein described in connection with apreferred embodiment, is liable of numerous variations without departingfrom its scope.

It is to be noted in particular that the invention is in no way limitedto thin housings such as the one hereinabove described, but includes onthe contrary any type of housings designed for containing at least onefragile element that it is desirable to assemble by means of a weldingmethod implementing vibrations having damaging amplitude for the fragileelement.

Similarly, the instant invention is not limited to housings comprisingan apparent connector. Particularly, the invention can apply to a logiccircuit carrier card comprising connection means of the electromagnetictype. In such a case, as in any case when the connections are notapparent, the invention permits to obtain such a card which has theadvantage of being fully airtight in addition to all the advantageshereinabove mentioned.

I claim:
 1. A housing, suitable for containing at least one fragileelement such as a logic circuit, comprising:two shells assembled byultrasonic welding, each shell comprising at least one welding areahaving a form permitting ultrasonic welding and being such that whenboth shells are assembled before welding a shift directed along avertical axis separates the shells; and at least one supporting platefor supporting a fragile element, said supporting plate comprising atleast one mounting portion, wherein at least one of the shells comprisesa receptacle for said mounting portion of the corresponding shell, andreceptacle and said mounting portion cooperating so that a movement ofthe supporting plate along transverse and axial axes is limited torespective transverse and axial clearances and movement of thesupporting plate of said two shells after welding along the verticalaxis is limited to a vertical clearance (JV).
 2. A housing according toclaim 1, wherein;at least one of said transverse and axial clearances isreduced to zero by said assembly and welding.
 3. A housing according toclaim 1, wherein:the mounting portion comprises a substantiallyparallelpipedic mounting ear extending in a transverse-axial plane, thereceptacle has a similar parallelpipedic shape, the relative sizes ofthe supporting plate, the mounting ear and the receptacle being suchthat the height of the ear is not greater than the total height of thereceptacle once the housing is assembled and welded, the ear comprisingon a transverse end adjacent the welding area a lateral face positionedin an axial-vertical plane with no contact possible between said lateralface and a corresponding face of the receptacle.
 4. A housing accordingto claim 1, wherein:a supporting plate is engaged in at least one notchin at least one of said shells, two mounting portions being provided,each mounting portion being associated with an end lateral face of asupporting plate, and said at least one notch comprises twocorresponding lateral faces, the relative size of the notch and of thesupporting plate being such that contact is prevented between said notchand said supporting plate, the end lateral faces of the supporting platebeing denied simultaneous contact with corresponding faces of the notch.5. A housing according to claim 1, wherein:the mounting portioncomprises a selected number of rounded edges.
 6. A housing according toclaim 1, wherein:the shells and the mounting portion are manufacturedfrom respective materials not liable to become amalgamated duringultrasonic welding of said at least two shells. .Iadd.
 7. A housingaccording to claim 1, wherein said housing has a square shape in thetransverse-axial plane..Iaddend..Iadd.8. A housing according to claim 1,wherein said housing has a rectangular shape in the transverse-axialplane..Iaddend..Iadd.9. A housing according to claim 1, furthercomprising a connector connected to said fragile element for releasablyconnecting said fragile element to an externalcircuit..Iaddend..Iadd.10. A housing according to claim 9, wherein saidconnector is attached to said supporting plate..Iaddend..Iadd.11. Ahousing, suitable for containing at least one fragile element such as alogic circuit, comprising:two shells assembled by welding, each shellcomprising at least one welding area having a form permitting weldingand being such that when both shells are assembled before welding ashift directed along a vertical axis separates the shells; and at leastone supporting plate for supporting a fragile element, said supportingplate comprising at least one mounting portion, wherein at least one ofthe shells comprises a receptacle for said mounting portion of thecorresponding shell, said receptacle and said mounting portioncooperating so that a movement of the supporting plate along transverseand axial axes is limited to respective transverse and axial clearancesand movement of the supporting plate of said two shells after weldingalong the vertical axis is limited to a vertical clearance(JV)..Iaddend..Iadd.12. A housing according to claim 11, wherein: theshells and the mounting portion are manufactured from respectivematerials not liable to be come amalgamated during welding of said twoshells..Iaddend..Iadd.13. A housing according to claim 11, wherein saidwelding is ultrasonic welding..Iaddend..Iadd.14. A housing according toclaim 13, wherein said shells are formed of ABS..Iaddend..Iadd.15. Ahousing according to claim 13, wherein said shells are formed ofnylon..Iaddend..Iadd.16. A housing according to claim 13, wherein saidshells are formed of ABS, and wherein said mounting portion is formed ofnylon..Iaddend..Iadd.17. A housing comprising: two shells assembled bywelding, each shell comprising at least one welding area having a formpermitting welding and being such that when both shells are assembledbefore welding a shift directed along a vertical axis separates theshells; and at least one supporting plate including at least onemounting portion, wherein at least one of the shells comprises areceptacle for said mounting portion of the corresponding shell, saidreceptacle and said mounting portion cooperating so that a movement ofthe supporting plate along transverse and axial axes is limited torespective transverse and axial clearances and movement of thesupporting plate of said two shells after welding along the verticalaxis is limited to a vertical clearance (JV)..Iaddend..Iadd.18. Ahousing according to claim 17, wherein: the shells and the mountingportion are manufactured from respective materials not liable to be comeamalgamated during welding of said two shells..Iaddend..Iadd.19. Ahousing according to claim 17, wherein said welding is ultrasonicwelding..Iaddend.